Mystery Clontarf Photo

Who are these men, briefly called to order to have their photo taken?  The only clues on the back of the photo are 'Clontarf' and '1905'.  Well, Edward and Jane Lane's Pleasure Gardens at Clontarf was the picnic venue of choice in the 1900s.  Among the groups to hold their annual picnics there in 1905 were: The Telegraph Construction Branch Union; the Amalgamated Slaughtermen; the United Friendly Societies; and the United Protestants.  They don't look like butchers on the spree, and telegraph engineers you would think would be a younger group.  Another group who let their hair down at Clontarf in April 1905 were the employees of Harrington and Co, photographic importers, just the very group to arrange to have a photo taken of themselves, you might think, but if this is them, where are the shop-girls?  And there is a suppressed merriment which sits uneasily with the idea of their being Orangemen.  Any ideas, anyone?  Full marks to the gent in the centre for his magnificent facial hair.

JMacR